This invention relates to electrochromic rearview mirrors for motor vehicles and, more particularly, to improved electrochromic rearview mirrors incorporating a third surface reflector/electrode in contact with at least one solution-phase electrochromic material.
Heretofore, various rearview mirrors for motor vehicles have been proposed which change from the full reflectance mode (day) to the partial reflectance mode(s) (night) for glare-protection purposes from light emanating from the headlights of vehicles approaching from the rear. Among such devices are those wherein the transmittance is varied by thermochromic, photochromic, or electro-optic means (e.g., liquid crystal, dipolar suspension, electrophoretic, electrochromic, etc.) and where the variable transmittance characteristic affects electromagnetic radiation that is at least partly in the visible spectrum (wavelengths from about 3800 xc3x85 to about 7800 xc3x85). Devices of reversibly variable transmittance to electromagnetic radiation have been proposed as the variable transmittance element in variable transmittance light-filters, variable reflectance mirrors, and display devices, which employ such light-filters or mirrors in conveying information. These variable transmittance light filters have included windows.
Devices of reversibly variable transmittance to electromagnetic radiation, wherein the transmittance is altered by electrochromic means, are described, for example, by Chang, xe2x80x9cElectrochromic and Electrochemichromic Materials and Phenomena,xe2x80x9d in Non-emissive Electrooptic Displays, A. Kmetz and K. von Willisen, eds. Plenum Press, New York, N.Y. 1976, pp. 155-196 (1976) and in various parts of Electrochromism, P. M. S. Monk, R. J. Mortimer, D. R. Rosseinsky, VCH Publishers, Inc., New York, N.Y. (1995). Numerous electrochromic devices are known in the art. See, e.g., Manos, U.S. Pat. No. 3,451,741; Bredfeldt et al., U.S. Pat. No. 4,090,358; Clecak et al., U.S. Pat. No. 4,139,276; Kissa et al., U.S. Pat. No. 3,453,038; Rogers, U.S. Pat. Nos. 3,652,149, 3,774,988 and 3,873,185; and Jones et al., U.S. Pat. Nos. 3,282,157, 3,282,158, 3,282,160 and 3,283,656.
In addition to these devices, there are commercially available electrochromic devices and associated circuitry, such as those disclosed in U.S. Pat. No. 4,902,108, entitled xe2x80x9cSINGLE-COMPARTMENT, SELF-ERASING, SOLUTION-PHASE ELECTROCHROMIC DEVICES SOLUTIONS FOR USE THEREIN, AND USES THEREOF,xe2x80x9d issued Feb. 20, 1990, to H. J. Byker; Canadian Patent No. 1,300,945, entitled xe2x80x9cAUTOMATIC REARVIEW MIRROR SYSTEM FOR AUTOMOTIVE VEHICLES,xe2x80x9d issued May 19, 1992, to J. H. Bechtel et al.; U.S. Pat. No. 5,128,799, entitled xe2x80x9cVARIABLE REFLECTANCE MOTOR VEHICLE MIRROR,xe2x80x9d issued Jul. 7, 1992, to H. J. Byker; U.S. Pat. No. 5,202,787, entitled xe2x80x9cELECTRO-OPTIC DEVICE,xe2x80x9d issued Apr. 13, 1993, to H. J. Byker et al.; U.S. Pat. No. 5,204,778, entitled xe2x80x9cCONTROL SYSTEM FOR AUTOMATIC REARVIEW MIRRORS,xe2x80x9d issued Apr. 20, 1993, to J. H. Bechtel; U.S. Pat. No. 5,278,693, entitled xe2x80x9cTINTED SOLUTION-PHASE ELECTROCHROMIC MIRRORS,xe2x80x9d issued Jan. 11, 1994, to D. A. Theiste et al.; U.S. Pat. No. 5,280,380, entitled xe2x80x9cUV-STABILIZED COMPOSITIONS AND METHODS,xe2x80x9d issued Jan. 18, 1994, to H. J. Byker; U.S. Pat. No. 5,282,077, entitled xe2x80x9cVARIABLE REFLECTANCE MIRROR,xe2x80x9d issued Jan. 25, 1994, to H. J. Byker; U.S. Pat. No. 5,294,376, entitled xe2x80x9cBIPYRIDINIUM SALT SOLUTIONS,xe2x80x9d issued Mar. 15, 1994, to H. J. Byker; U.S. Pat. No. 5,336,448, entitled xe2x80x9cELECTROCHROMIC DEVICES WITH BIPYRIDINIUM SALT SOLUTIONS,xe2x80x9d issued Aug. 9, 1994, to H. J. Byker; U.S. Pat. No. 5,434,407, entitled xe2x80x9cAUTOMATIC REARVIEW MIRROR INCORPORATING LIGHT PIPE,xe2x80x9d issued Jan. 18, 1995, to F. T. Bauer et al.; U.S. Pat. No. 5,448,397, entitled xe2x80x9cOUTSIDE AUTOMATIC REARVIEW MIRROR FOR AUTOMOTIVE VEHICLES,xe2x80x9d issued Sep. 5, 1995, to W. L. Tonar; and U.S. Pat. No. 5,451,822, entitled xe2x80x9cELECTRONIC CONTROL SYSTEM,xe2x80x9d issued Sep. 19, 1995, to J. H. Bechtel et al. Each of these patents is commonly assigned with the present invention and the disclosures of each, including the references contained therein, are hereby incorporated herein in their entirety by reference. Such electrochromic devices may be utilized in a fully integrated inside/outside rearview mirror system or as separate inside or outside rearview mirror systems.
FIG. 1 shows a typical electrochromic mirror device 10, having front and rear planar elements 12 and 16, respectively. A transparent conductive coating 14 is placed on the rear face of the front element 12, and another transparent conductive coating 18 is placed on the front face of rear element 16. A reflector (20a, 20b and 20c), typically comprising a silver metal layer 20a covered by a protective copper metal layer 20b, and one or more layers of protective paint 20c, is disposed on the rear face of the rear element 16. For clarity of description of such a structure, the front surface of the front glass element is sometimes referred to as the first surface, and the inside surface of the front glass element is sometimes referred to as the second surface. The inside surface of the rear glass element is sometimes referred to as the third surface, and the back surface of the rear glass element is sometimes referred to as the fourth surface. The front and rear elements are held in a parallel and spaced-apart relationship by seal 22, thereby creating a chamber 26. The electrochromic medium 24 is contained in space 26. The electrochromic medium 24 is in direct contact with transparent electrode layers 14 and 18, through which passes electromagnetic radiation whose intensity is reversibly modulated in the device by a variable voltage or potential applied to electrode layers 14 and 18 through clip contacts and an electronic circuit (not shown).
The electrochromic medium 24 placed in space 26 may include surface-confined, electrode position-type or solution-phase-type electrochromic materials and combinations thereof. In an all solution-phase medium, the electrochemical properties of the solvent, optional inert electrolyte, anodic materials, cathodic materials, and any other components that might be present in the solution are preferably such that no significant electrochemical or other changes occur at a potential difference which oxidizes anodic material and reduces the cathodic material other than the electrochemical oxidation of the anodic material, electrochemical reduction of the cathodic material, and the self-erasing reaction between the oxidized form of the anodic material and the reduced form of the cathodic material.
In most cases, when there is no electrical potential difference between transparent conductors 14 and 18, the electrochromic medium 24 in space 26 is essentially colorless or nearly colorless, and incoming light (Io) enters through front element 12, passes through transparent coating 14, electrochromic containing chamber 26, transparent coating 18, rear element 16, and reflects off layer 20a and travels back through the device and out front element 12. Typically, the magnitude of the reflected image (IR) with no electrical potential difference is about 45 percent to about 85 percent of the incident light intensity (Io). The exact value depends on many variables outlined below, such as, for example, the residual reflection (Ixe2x80x2R) from the front face of the front element, as well as secondary reflections from the interfaces between: the front element 12 and the front transparent electrode 14, the front transparent electrode 14 and the electrochromic medium 24, the electrochromic medium 24 and the second transparent electrode 18, and the second transparent electrode 18 and the rear element 16. These reflections are well known in the art and are due to the difference in refractive indices between one material and another as the light crosses the interface between the two. If the front element and the back element are not parallel, then the residual reflectance (Ixe2x80x2R) or other secondary reflections will not superimpose with the reflected image (IR) from mirror surface 20a, and a double image will appear (where an observer would see what appears to be double (or triple) the number of objects actually present in the reflected image).
There are minimum requirements for the magnitude of the reflected image depending in whether the electrochromic mirrors are placed on the inside or the outside of the vehicle. For example, according to current requirements from most automobile manufacturers, inside mirrors preferably have a high end reflectivity of at least 70 percent, and outside mirrors must have a high end reflectivity of at least 35 percent.
Electrode layers 14 and 18 are connected to electronic circuitry which is effective to electrically energize the electrochromic medium, such that when a potential is applied across the transparent conductors 14 and 18, electrochromic medium in space 26 darkens, such that incident light (Io) is attenuated as the light passes toward the reflector 20a and as it passes back through after being reflected. By adjusting the potential difference between the transparent electrodes, such a device can function as a xe2x80x9cgray-scalexe2x80x9d device, with continuously variable transmittance over a wide range. For solution-phase electrochromic systems, when the potential between the electrodes is removed or returned to zero, the device spontaneously returns to the same, zero-potential, equilibrium color and transmittance as the device had before the potential was applied. Other electrochromic materials are available for making electrochromic devices. For example, the electrochromic medium may include electrochromic materials that are solid metal oxides, redox active polymers, and hybrid combinations of solution-phase and solid metal oxides or redox active polymers; however, the above-described solution-phase design is typical of most of the electrochromic devices presently in use.
Even before a fourth surface reflector electrochromic mirror was commercially available, various groups researching electrochromic devices had discussed moving the reflector from the fourth surface to the third surface. Such a design has advantages in that it should, theoretically, be easier to manufacture because there are fewer layers to build into a device, i.e., the third surface transparent electrode is not necessary when there is a third surface reflector/electrode. Although this concept was described as early as 1966, no group had commercial success because of the exacting criteria demanded from a workable auto-dimming mirror incorporating a third surface reflector. U.S. Pat. No. 3,280,701, entitled xe2x80x9cOPTICALLY VARIABLE ONE-WAY MIRROR,xe2x80x9d issued Oct. 25, 1966, to J. F. Donnelly et al. has one of the earliest discussions of a third surface reflector for a system using a pH-induced color change to attenuate light.
U.S. Pat. No. 5,066,112, entitled xe2x80x9cPERIMETER COATED, ELECTRO-OPTIC MIRROR,xe2x80x9d issued Nov. 19, 1991, to N. R. Lynam et al., teaches an electro-optic mirror with a conductive coating applied to the perimeter of the front and rear glass elements for concealing the seal. Although a third surface reflector is discussed therein, the materials listed as being useful as a third surface reflector suffer from one or more of the following deficiencies: not having sufficient reflectivity for use as an inside mirror, or not being stable when in contact with a solution-phase electrochromic medium containing at least one solution-phase electrochromic material.
Others have broached the topic of a reflector/electrode disposed in the middle of an all solid state-type device. For example, U.S. Pat. Nos. 4,762,401, 4,973,141, and 5,069,535 to Baucke et al. teach an electrochromic mirror having the following structure: a glass element, a transparent (ITO) electrode, a tungsten oxide electrochromic layer, a solid ion conducting layer, a single layer hydrogen ion-permeable reflector, a solid ion conducting layer, a hydrogen ion storage layer, a catalytic layer, a rear metallic layer, and a back element (representing the conventional third and fourth surface). The reflector is not deposited on the third surface and is not directly in contact with electrochromic materials, certainly not at least one solution-phase electrochromic material and associated medium. Consequently, it is desirable to provide an improved high reflectivity electrochromic rearview mirror having a third surface reflector/electrode in contact with a solution-phase electrochromic medium containing at least one electrochromic material.
In the past, information, images or symbols from displays, such as vacuum fluorescent displays, have been displayed on electrochromic rearview mirrors for motor vehicles with reflective layers on the fourth surface of the mirror. The display is visible to the vehicle occupant by removing all of the reflective layer on a portion of the fourth surface and placing the display in that area. Although this design works adequately due to the transparent conductors on the second and third surface to impart current to the electrochromic medium, presently no design is commercially available which allows a display device to be incorporated into a mirror that has a reflective layer on the third surface. Removing all of the reflective layer on the third surface in the area aligned with the display area or the glare sensor area causes severe residual color problems when the electrochromic medium darkens and clears because, although colorization occurs at the transparent electrode on the second surface, there is no corresponding electrode on the third surface in that corresponding area to balance the charge. As a result, the color generated at the second surface (across from the display area or the glare sensor area) will not darken or clear at the same rate as other areas with balanced electrodes. This color variation is significant and is very aesthetically unappealing to the vehicle occupants.
Similar problems exist for outside rearview mirror assemblies that include signal lights, such as turn signal lights, behind the rear surface of the mirror. Examples of such signal mirrors are disclosed in U.S. Pat. Nos. 5,207,492, 5,361,190, and 5,788,357. By providing a turn signal light in an outside mirror assembly, a vehicle, or other vehicles travelling in the blind spot of the subject vehicle, will be more likely to notice when the driver has activated the vehicle""s turn signal and thereby attempt to avoid an accident. Such mirror assemblies typically employ a dichroic mirror and a plurality of red LEDs mounted behind the mirror as the signal light source. The dichroic mirror includes a glass substrate and a dichroic reflective coating provided on the rear surface of the glass plate that transmits the red light generated by the LEDs as well as infrared radiation while reflecting all light and radiation having wavelengths less than that of red light. By utilizing a dichroic mirror, such mirror assemblies hide the LEDs when not in use to provide the general appearance of a typical rearview mirror, and allow the red light from such LEDs to pass through the dichroic mirror and be visible to drivers of vehicles behind and to the side of the vehicle in which such a mirror assembly is mounted. Examples of such signal mirrors are disclosed in U.S. Pat. Nos. 5,361,190 and 5,788,357.
In daylight, the intensity of the LEDs must be relatively high to enable those in other vehicles to readily notice the signal lights. Because the image reflected toward the driver is also relatively high in daylight, the brightness of the LEDs is not overly distracting. However, at night the same LED intensity could be very distracting, and hence, potentially hazardous. To avoid this problem, a day/night sensing circuit is mounted in the signal light subassembly behind the dichroic mirror to sense whether it is daytime or nighttime and toggle the intensity of the LEDs between two different intensity levels. The sensor employed in the day/night sensing circuit is most sensitive to red and infrared light so as to more easily distinguish between daylight conditions and the bright glare from the headlights of a vehicle approaching from the rear. Hence, the sensor may be mounted behind the dichroic coating on the dichroic mirror.
The dichroic mirrors used in the above-described outside mirror assemblies suffer from the same problems of many outside mirror assemblies in that their reflectance cannot be dynamically varied to reduce nighttime glare from the headlights of other vehicles.
Although outside mirror assemblies exist that include signal lights and other outside mirror assemblies exist that include electrochromic mirrors, signal lights have not been provided in mirror assemblies having an electrochromic mirror because the dichroic coating needed to hide the LEDs of the signal light typically cannot be applied to an electrochromic mirror, particularly those mirrors that employ a third surface reflector/electrode.
Accordingly, it is an aspect of the present invention to solve the above problems by providing an electrochromic rearview mirror assembly that includes a third surface reflector/electrode that provides a continuous layer of electrically conductive material across the entire visible surface of the rear element of the mirror, even those regions that lie in front of a light source, such as a signal light, information display, or illuminator, or a light sensor or receptor, that is positioned behind the electrochromic mirror. Yet another aspect of the present invention is to provide an electrochromic mirror having a third surface reflector/electrode that is at least partially transmissive at least in regions in front of a light source, such as a display, illuminator, or signal light. An additional aspect of the present invention is to provide a third surface reflector/electrode (i.e., second electrode) that is at least partially reflective in those regions in front of the light source so as to provide an ascetically pleasing appearance. Still another aspect of the present invention is to provide a coating for the third surface of an electrochromic mirror that functions as an electrode and as a reflector while allowing light having wavelengths corresponding to a display to be transmitted through the mirror. Still another aspect of the present invention is to provide an electrochromic mirror having a partially reflective, partially transmissive electrode that does not have too yellow a hue and has relative color neutrality.
To achieve these and other aspects and advantages, the electrochromic mirror according to the present invention comprises front and rear elements having front and rear surfaces and being sealably bonded together in a spaced-apart relationship to define a chamber; a transparent first electrode including a layer of conductive material carried on a surface of one of the elements; an electrochromic material contained in the chamber; and a partially transmissive, partially reflective second electrode disposed over substantially all of the front surface of the rear element. The electrochromic rearview mirror so constructed, has a reflectance of at least about 35% and a transmittance of at least about 5% in at least portions of the visible spectrum. The mirror preferably further exhibits relative color neutrality with a C* value of less than about 20. Further, the mirror preferably does not have a perceivable yellow hue and thus has a b* value less than about 15.
Another aspect of the present invention is to provide a rearview mirror assembly having a light emitting display assembly mounted behind the mirror within the mirror housing whereby spurious reflections and ghost images are substantially reduced or eliminated. To achieve this and other aspects and advantages, a rearview mirror assembly according to the present invention comprises a housing adapted to be mounted to the vehicle; front and rear elements mounted in the housing, the elements each having front and rear surfaces and being sealably bonded together in a spaced-apart relationship to define a chamber; an electrochromic material contained in the chamber; a transparent first electrode including a layer of conductive material carried on a surface of one of the elements; a second electrode disposed on the front surface of the rear element; and a light emitting display mounted in the housing. Either the second electrode is reflective or a separate reflector is provided on the rear surface of the rear element, the reflective electrode/reflector being at least partially transmissive in at least a location in front of the display. The display has a front surface and is preferably mounted behind the rear surface of the rear element, such that the front surface of the display is not parallel with the rear surface of the mirror. Alternatively, the display may have a non-specular front surface or the front surface could be laminated directly onto the back of the mirror. As yet another alternative, an anti-reflection coating may be applied to the reflective surface(s) of the display and the front surface of the mirror. Still another alternative to achieve the above aspects and advantages is to provide at least one masking component that minimizes light that is emitted from the display from reflecting off of the reflector back toward the display and then reflecting back off the front surface of the display toward the front surface of the front element then on to the viewer.
An additional aspect of the present invention is to provide a rearview mirror assembly including a light emitting display, whereby the display is mounted in front of the reflective layer of the mirror. To achieve these and other aspects of the present invention, a light emitting display may be used that is substantially transparent and mounted either to the front surface of the front element or mounted in the chamber defined between the front and rear elements. A preferred transparent light emitting display is an organic light emitting diode display.
Another aspect of the present invention is to provide an exterior rearview mirror assembly incorporating a light source for illuminating a portion of the exterior of the vehicle, such as the door handle and locking mechanism area of a vehicle door. To achieve these and other aspects and advantages, an exterior rearview mirror assembly of the present invention comprises a housing adapted to be mounted to the exterior of the vehicle; a first element mounted in the housing, the element having a front and rear surface; a reflector disposed on one of the surfaces of the first element; and a light source mounted in the housing behind the rear surface of the first element, the light source being positioned within the housing so as to emit light, when activated, through the first element and through a region of the reflector that is at least partially transmissive toward a side of a vehicle. Such a rearview mirror assembly thus conveniently illuminates areas on the outside of the vehicle such as the door handles and locking mechanisms.
Another aspect of the invention is to locate a light sensor, such as that used to sense ambient light in an electrochromic mirror assembly, behind a reflective portion of the mirror while providing for increased sensing area for light collection behind the electrochromic media and reflective portion of the mirror without the distractive appearance resulting from missing patches of reflective material in the mirror. To achieve these and other aspects and advantages, an electrochromic mirror of the present invention comprises a housing adapted to be mounted to the vehicle; front and rear elements mounted in said housing, the elements each having front and rear surfaces and being sealably bonded together in a spaced-apart relationship to define a chamber; a transparent first electrode including a layer of conductive material carried on a surface of one of the elements; a second electrode disposed on the front surface of the rear element, wherein either said second electrode is a reflective electrode or a separate reflector is disposed over substantially all of the rear surface of the rear element, the reflective electrode/reflector being partially transmissive and partially reflective over substantially all of one of the surfaces of the rear element; an electrochromic material contained in the chamber; and a light sensor mounted in the housing behind the rear element and behind the partially transmissive, partially reflective electrode/reflector.
In accordance with another embodiment of the present invention, a rearview mirror assembly for a vehicle comprises: a housing adapted to be mounted to the vehicle; front and rear elements mounted in the housing, the elements each having front and rear surfaces and being sealably bonded together in a spaced-apart relationship to define a chamber; a transparent first electrode including a layer of conductive material carried on a surface of one of the elements; a second electrode disposed on the front surface of the rear element; an electrochromic material contained in the chamber; and a graphic display positioned in the housing behind said rear element, wherein either the second electrode is a reflective electrode or a separate reflector is disposed over substantially all of the rear surface of the rear element, the reflective electrode/reflector being partially transmissive and partially reflective in at least a location in front of the graphic display.
These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.